The invention relates to chromatographic separation and fractionation.
A chromatography column can be used to separate different compounds in a sample being flushed through the column in a solvent. The different compounds in the sample are delayed in passage through the column to different extents and exit the column at different times. A fraction collector directs a first part of the sample leaving the column to one fraction-collecting well, the second part to a second well and so on. A detector can be used to detect absorption or another characteristic of the sample during the processing of the sample downstream of the column and upstream of the fraction collector in order to detect the presence of different compounds in the stream from the column and to decide when to begin and terminate collection, and when to advance the fraction collector to a new well.
In a chromatography system available from the Biotage Inc. under the Parallex Flex and Horizon designation, sampling can be initiated and terminated based upon the UV absorbance values or based upon the slopes of these values over time. A fraction cut can be triggered by collected volume (i.e., when a well has been filled to capacity) and by detection of a valley between peaks based upon detection of a change in slope from a negative value to a positive value.
In one aspect, the invention features, in general, a chromatography system including a chromatography column connected to receive a sample and separate different compounds in the sample, a detector that outputs a signal indicating the presence of compounds in the sample leaving the column, a fraction collector that directs fractions of the sample from the column to separate fraction wells, and an electronic controller that receives inputs from the detector and controls the fraction collector. The electronic controller monitors the signal from the detector over time and initiates a cut from one well to another at the fraction collector when the signal over time experiences a shoulder where the slope of the signal over time does not change in sign but does change by more than a predetermined amount, and the slope is negative.
In another aspect, the invention features, in general, a chromatography system including a chromatography column, a flow-through detector, and a fraction collector as already described. The system also includes an electronic controller that monitors the signal from the detector over time and initiates a cut from one well to another at the fraction collector when the slope is positive and experiences a shoulder as determined by a positive slope at one point in time that is less than a slope threshold, and a positive slope at a later time that is greater than X times the slope threshold, where X is greater than one (preferably greater than 1.5 and most preferably between 1.5 and 2.5).
In another aspect, the invention features, in general, a chromatography system including a chromatography column, a flow-through detector, and a fraction collector. The system also includes an electronic controller that monitors the signal from the detector over time and initiates a cut from one well to another at the fraction collector when the signal is less than a slope detection disable threshold and the signal over time experiences a specified change in slope condition.
In another aspect, the invention features, in general, a chromatography system including a chromatography column, a flow-through detector, and a fraction collector. The system also includes an electronic controller that monitors the signal from the detector over time and identifies valleys in the signal from the detector over time. The system also includes a user interactive display and input device that permits the user to select whether or not to collect during valleys in the signal over time, and the controller either ends collection after identifying a valley or causes a fraction cut at a set time.
In another aspect, the invention features, in general a chromatography system including a chromatography column, a flow-through detector, a fraction collector, and an electronic controller that monitors the signal from the detector over time. The system also includes a user interactive display and input device that permits the user to select to operate in a custom mode in which the user determines setpoint conditions for initiating and ending collection or to operate in one of a set of preset collection modes in which the setpoint conditions for initiating and ending collection are preset.
Preferred embodiments of the invention may include one or more of the following features. In preferred embodiments the electronic controller determines if the signal is in a valley by the slope being positive at a set time delay past the cut when the slope is negative. The controller can cause the fraction collector to move to a new well after the set time delay. Alternately the controller can end collection after the set time delay. The system includes a user interactive display and input device that permits the user to enter the slope threshold, the slope disable detection threshold, the set time delay, and a threshold value for the signal for the controller to initiate and stop collection. The detector emits a signal measuring characteristics of the compound. For example, a UV absorbance detector emits a signal measuring the UV absorbance.
Embodiments of the invention may include one or more of the following advantages. The detection based on UV slope and changes in UV slope allows for more fine tuned control of the fractionation process, leading to higher purity in the chemical compounds collected and higher efficiencies. The user can enter various data to control the stop/start and cut point decision analysis, or can alternatively rely on preselected modes of operation.
Other advantages and features of the invention will be apparent from the following description of a particular embodiment and from the claims.